视频:你真的需要低延迟流媒体吗?

While low 延迟 is a goal for all live streaming applications, commonly associated with reliability and a better user experience, reducing 延迟 also increases the expense of delivering large-scale streams. In this excerpt from his presentation at 流媒体 East 2017, Wowza VP of Product and User Experience Mike Talvensaari argues that low 延迟 isn't always worth it, 并且您应该只在某些用例中优先考虑它.

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Mike Talvensaari: We hear terms like low 延迟, ultra-low 延迟, real time. 当我们谈论这些事情时，我们真正想表达的是什么? So I'm going to start at the left combination for the latencies for HLS and DASH. These are upwards of 45 seconds, 30-45 seconds depending in you're going through a CDN. 这是面向大量观众的单向流媒体. I have to have massive scale, people want to see it in HD, or 4K. 所以我可以在这里处理延迟. 减少的延迟大约是5到20秒. 最近秒. And this would be live streaming of 新闻, 体育, and content for OTT providers.

低延时. 5-7秒是高清有线电视的典型延迟. 所以我们称比这快的东西为低延迟. 这是针对直播的, 游戏流, E-体育--sometimes you want to try to match that 5-second delay if you're streaming television content. So it matches up with what people are seeing if they're watching on TV. 你想喊“进球”!” at the same time as your neighbor if you're watching a sporting event.

近实时时间小于1秒. 这将用于实时通信, 会议, 任何形式的远程呈现, 实时设备控制. I'm controlling a PTZ camera, I want to hit the button and see it pan right immediately. 这是近乎实时的. 这是一些定义.

People think they need really low 延迟 streaming all the time but they don't necessarily need it. So in designing your system, if you want low 延迟, it's just going to cost more. 你将不得不购买更昂贵的设备. 你需要更多的服务器. 更高质量，更高带宽. 但你通常不需要更低的延迟. 30秒的延迟通常不是问题.

所以延迟并不重要. 所以要认真考虑，我是否需要低延迟? 我的用例需要低延迟吗? 如果我在直播高中体育比赛, does it really matter if grandma in California sees it 30 seconds delayed or not? 可能不重要.

HTTP流媒体, 现在最流行的流媒体格式是什么, 有意引入延迟以提高可靠性. So Apple HLS and MPEG-DASH, both by default out of the box require three chunks to be loaded. The chunks are 10 seconds, that gives you a huge buffer of time for network hiccups. Buffering has been greatly reduced over the years due to things ... 像这样. 因此，这些东西的可靠性得到了提高.

对于一些实时流，延迟是至关重要的. 如果你正在进行实时交流，这是至关重要的. 任何超过一秒的事都是痛苦的. If you're doing 网络游戏, any sort of remote control devices ... gambling, auctions, 延迟 is critical for certain use cases.